Remove slow array copy from math.floor()
Explicitly use real literals in floor/ceil tests
Add float/double overloads for floor/ceil
Move common floor() code into floorImpl()
Convert isNan/isInfinite into generic functions, add compile-time float path
Replace BMASK with a computed clear mask
Merge pull request #2274 from ibuclaw/floormath

Improvements to std.math floor() / ceil()